I'm very interested in dwarf loaches... never see them around here though- and couldn't afford them even if I did! 
As for substrate- I'm using a natural looking play sand- but in research I found the coloured play sand by crayola sold at Walmart is safe for aquariums
I did STRONGLY consider the purple sand because I intend to get Red cherry shrimp and the purple would have helped bring out the colour. (and of their fish tankmates).
I did instead go for the natural look- and hope the shrimp will forgive me for having a light-coloured substrate! (plenty of shade and hiding spots and dark slate caves).
Anyhow- back on topic with the loaches... they truly are a fantastic find- one of the best looking fish around.
Now hurry up and breed them so I can buy some off you.

As for substrate- I'm using a natural looking play sand- but in research I found the coloured play sand by crayola sold at Walmart is safe for aquariums
I did STRONGLY consider the purple sand because I intend to get Red cherry shrimp and the purple would have helped bring out the colour. (and of their fish tankmates).
I did instead go for the natural look- and hope the shrimp will forgive me for having a light-coloured substrate! (plenty of shade and hiding spots and dark slate caves).
Anyhow- back on topic with the loaches... they truly are a fantastic find- one of the best looking fish around.
Now hurry up and breed them so I can buy some off you.